The invention relates to compositions comprising urethane resins, in particular, amine-terminated urethane oligomers. The invention further relates to polymers prepared by combining urethane oligomers with crosslinking agents and to coatings formed from the resulting polymers.
Polyurethanes are used in a variety of commercial applications for the production of products such as fibers, adhesives, coatings, elastomers and foams. Polyurethane coatings can have desirable properties including high gloss, chemical resistance and abrasion resistance. Preferred urethane coatings also display flexibility, impact resistance, and toughness. For use as coatings, the composition must be prepared in a form that can be spread on the relevant surface. The curing or crosslinking process then completes polymer formation as any remaining volatiles evaporate.
Urethane coatings can be supplied in the form of a two component formulation, where the two components are mixed prior to application to a surface. One component includes urethane oligomers with suitable functional groups available for crosslinking. The second component includes a crosslinking agent that can react with the functional groups of the urethane oligomers.
The present invention involves the formation of compositions with very high concentrations of amine-terminated urethane oligomers. The oligomers of compositions generally are unsolvated. The compositions can include plasticizers, viscosity modifiers and other additives. The compositions generally have sufficiently low viscosities such that they can be blended with appropriate crosslinking compositions to form desirable polymers. The high solid, urethane oligomer compositions have improved properties for the formation of coatings. In particular, the polymer compositions can be applied in relatively thick layers without hindering the curing process to form high quality coatings.
In a first aspect, the invention features a composition including greater than about 55 percent by weight amine-terminated urethane oligomers. In selected embodiments the composition includes from about 60 percent to about 90 percent by weight amine-terminated urethane oligomers. In other embodiments the composition includes from about 65 percent to about 80 percent by weight amine-terminated urethane oligomers.
The composition can further include an aqueous viscosity modifying agent. The aqueous viscosity modifying agent can include greater than about 30 percent by weight volatile alcohol. The composition also can include volatile organic acids, with the composition preferably comprising less than about 10 percent and more preferably less than about 1 percent by mole equivalent of carboxylate groups of the volatile organic acids relative to amine groups of the amine-terminated urethane oligomers. The amine-terminated urethane oligomers can include primary amine-terminated oligomers. The amine-terminated urethane oligomers can include multifunctional amine moieties bonded at secondary amine sites to isocyanate functional groups of a urethane oligomer to form carbamate linkages. Suitable multifunctional amine moieties include N-(aminoethyl) piperazine moieties.
In another aspect, the invention features a kit including:
a) a composition comprising greater than about 55 percent by weight amine-terminated urethane oligomers; and
b) a polyepoxide compound in a container separate from the composition comprising amine-terminated urethane oligomers.
The polyepoxide can be a polyglycidyl ether of a polyphenol, a polyglycidyl ether of aliphatic polyol with 2 to 4 hydroxyl groups, or mixtures thereof. The ratio of active hydrogens in amine functional groups to epoxide groups preferably ranges from about 1:1 to about 1.75:1.
In another aspect, the invention features a method of producing an amine-terminated urethane oligomer composition comprising the steps of
a) adding water to a polyketimine functionalized urethane oligomer; and
b) removing ketone to form a composition comprising greater than about 55 percent by weight amine-terminated urethane oligomer.
In another aspect, the invention features a polymer coating including an epoxy crosslinked amine-terminated urethane polymer, the coating being formed by curing a mixture of polyepoxides and a composition comprising greater than about 55 percent by weight amine-terminated urethane oligomers.
In another aspect, the invention features a method of forming a coating comprising the steps of spreading a mixture on a surface such that it can cure, the mixture obtained by mixing polyepoxides with a composition comprising greater than about 55 percent by weight amine-terminated urethane oligomers. The surface can be concrete and can form a wall or a floor.